The processing of workpieces such as semiconductor wafers and magnetic discs often includes processes such as polishing, honing, lapping, or grinding. Flat honing, lapping, and polishing (hereinafter referred to as honing) typically involve passing a surface of a workpiece over a honing member such as a honing stone, a grinding stone, or a polishing pad. In addition to the honing member, a polishing or grinding agent may be present during the honing process. Examples of polishing or grinding agents include slurries, lubricants and water.
A carrier is often used to support the workpiece during the honing process. The carrier is generally configured to work in conjunction with a particular honing machine. A typical carrier has an aperture or recess configured to receive a workpiece. In addition, the carrier generally has gear teeth that correspond to gear teeth on one or more drive wheels of the honing machine. In this case, the honing or grinding occurs when the gear teeth on the drive wheels of the honing machine cause the workpiece carrier to move relative to the honing member. Typically, the movement of the carrier may be translational, rotational, or a combination thereof. A typical carrier is disclosed in U.S. Pat. No. 5,085,009, issued on Feb. 4, 1992 to Kinumura et al.
During the polishing process, one or more workpieces typically resides within the aperture(s) formed in the carrier. As the diameters of the apertures in the carriers are usually slightly larger than the outside diameters of the workpieces, the workpieces often move slightly within the apertures during polishing. If the material of which the carrier is constructed is harder than the material of which the workpiece is constructed, such movement may cause the surface of the workpiece to become undesirably scratched. Accordingly, it would be desirable to fabricate the carrier from a soft, flexible material, but softer materials often cannot withstand the stress of a polishing or honing process. Therefore, it is desirable to coat the inside edge of a stiff carrier with a material resistant to damaging the workpieces.
Carriers presently used to polish or hone workpieces are generally made from fiberglass, thin metal sheets or thin metal sheets coated with fiberglass. Use of metal is desirable as it provides a strong, stiff core and facilitates formation of gear teeth. However, as mentioned above, use of metal which is harder than the surface of the workpiece may cause scratching of the workpiece during processing. Such scratching can be prevented by coating the metal core with a softer material, such as fiberglass or the like.
A fiberglass-coated carrier is typically made by first creating the metal core by cutting gear teeth and apertures into a metal sheet. All dimensions and surfaces of the metal core are then filled or coated with the fiberglass material, for example, prepeg fiberglass laminate. Next, gear teeth and apertures are cut into the fiberglass material in substantially the same locations as the gear teeth and apertures in the metal core. Since the inside diameters of the fiberglass apertures are slightly smaller than the inside diameters of the metal core, it is the softer, more forgiving fiberglass material that contacts the workpiece.
Presently known methods of making coated metal carriers suffer from several shortcomings. One is that it is sometimes very difficult to align the fiberglass cut of the gear teeth with the metal gear teeth cut. Also, the gear teeth cannot be cut in the metal and fiberglass at the same time, because the bond between the fiberglass and the metal is not strong enough to withstand the tooth cutting process; i.e., the fiberglass delaminates from the metal surface when the gear teeth are simultaneously formed in both materials. Another drawback of known fiberglass coated carriers is that the fiberglass tends to break or chip off during the processing of the workpieces. These small fiberglass particles that break off may contact and scratch the surface of the workpiece and contaminate the polish pad. An improved workpiece carrier that overcomes the short comings of the prior art is desirable.